The present invention relates to liquid crystal devices and manufacturing method thereof and, more particularly, to a novel liquid crystal device and manufacturing method for same, with a long life time of the device available at a low cost.
Liquid crystal devices such as compact displays having light weight are broadly used in the fields of microcomputers, word processors, compact television system or so on. For instance, the display operates best in the parallel nematic configuration. wherein the elongated axes of both the liquid crystal molecules, light-absorbing dichroic dye molecules are aligned in the same direction parallel to the wall of the display cell, in the electrically unexcited state. In this condition, the molecules in cooperation with polarizer absorb the majority of incident light, and render the background of the display, as well as any unactivated pixels, to a dark condition. The pixels are electrically excited to align the molecules perpendicular to the cell walls and achieve less-absorbing state displaying relatively bright area against the dark background. Thus, the pixels can be energized between bright and dark conditions.
Such liquid crystal displays are usefull especially for a diplay a large panel area which includes 200.times.400 pixels for example. As one of liquid crystals available for the displays, twisted nematic type has been used frequently. Liquid crystal of this type is not so susceptible to impurity such as alkali metal contained in opposed glass substrates, especially impurity phosphorus or boron.
Recently, on the other hand, liquid crystals of other type has been reported as promising materials for some liquid crystal appliances. For instance, chiral smectic phase is coming to fruition in some fields. The smectic phase, however, imparts high viscosity to liquid crystal at a room temperature so that it is necessary to lower the viscosity by raising the temperature of the liquid crystal up to 120.degree. to 150 C..degree. to charge the liquid crystal into the narrow space between opposed substrates. Because of this, the high temperature undesirably promotes diffusion of impurity such as sodium into the liquid crystal from a conductive transparent electrode or a glass substrate contiguous to the liquid crystal. In case of a passive device, both the opposed insides of the substrates are in contact with the liquid crystal, making the device degraded during long time use at a range between a room temperature and 50C..degree.. In case of active device, while the active element provision side of the device can be covered with a high purified polyimide, the opposite inside is exposed to the liquid crystal.